3D Microstructures of Liquid Crystal Networks with Programmed Voxelated Director Fields

Abstract

The shape‐shifting behavior of liquid crystal networks (LCNs) and elastomers (LCEs) is a result of an interplay between their initial geometrical shape and their molecular alignment. For years, reliance on either one‐step in situ or two‐step film processing techniques has limited the shape‐change transformations from 2D to 3D geometries. The combination of various fabrication techniques, alignment methods, and chemical formulations developed in recent years has introduced new opportunities to achieve 3D‐to‐3D shape‐transformations in large scales, albeit the precise control of local molecular alignment in microscale 3D constructs remains a challenge. Here, the voxel‐by‐voxel encoding of nematic alignment in 3D microstructures of LCNs produced by two‐photon polymerization using high‐resolution topographical features is demonstrated. 3D LCN microstructures (suspended films, coils, and rings) with designable 2D and 3D director fields with a resolution of 5 µm are achieved. Different shape transformations of LCN microstructures with the same geometry but dissimilar molecular alignments upon actuation are elicited. This strategy offers higher freedom in the shape‐change programming of 3D LCN microstructures and expands their applicability in emerging technologies, such as small‐scale soft robots and devices and responsive surfaces.

Smart Polymers for Microscale Machines

“…demonstrated helical and other structures with nonuniaxially alignment of mesogens programmed by pixelated microchannels which hold great potential to be used for microrobots. [ 123 ]…”

“…Recently, a microchannel with pixelated blocks was utilized to obtain more pattern flexibility. [ 123 ]…”

“…[ 156 ] It is also said that the swelling by an isotropic solvent is anisotropic because of the perpendicular direction to the director shows larger swelling and deformation. [ 123 ] Humidity responsiveness works because of the same mechanism. However, humidity absorption needs to be promoted by making the structure humidity sensitive.…”

“…recently. [ 123 ] Helical structures with a length of ≈150 µm were fabricated by DLW with pixelated microchannel cells. This pixelated microchannel helps positioning of printing location and structures with higher consistency can be achieved.…”

Liquid Crystal Elastomer‐Based Magnetic Composite Films for Reconfigurable Shape‐Morphing Soft Miniature Machines

“…DOI: 10.1002/adma.202006191 external stimuli, e.g., light, [1][2][3][4] heat, [5][6][7][8] and magnetic field, [9][10][11][12][13][14] via shape-morphing, show great potential in novel actuators. In particular, liquid crystal elastomers (LCEs) stand out from others due to the programmable, reversible, and large mechanical deformation capabilities induced by multiple external inputs, including light, [1][2][3][4] heat, [5][6][7][8] chemical solvent, [15] and electric fields. [16] LCEs are soft crosslinked polymers composed of anisotropic molecules called mesogens with predesigned molecular orientations.…”